To assess the feasibility of "tissue" expansion as a means of midface advancement for correction of hypoplasia, expanders were placed in the left maxillary sinuses of New Zealand White rabbits. Twenty-one animals were used for the study, all of whom underwent implantation of radiopaque dental amalgam markers adjacent to cranial sutures at 9 days of age. The nonoperative control group (n = 13) underwent no further surgery. At 30 days of age, the experimental group (n = 8) underwent placement of an inflatable 1-mL Silastic tissue expander in the left maxillary sinus. After 1 week, inflation was begun in serial increments of 0.15-mL normal saline to a total volume of approximately 1.05 mL over a 2-week period. Lateral cephalometrograms were obtained at 9, 30, 60, and 90 days of age to measure growth of the craniofacial skeleton. Both groups demonstrated similar growth between 9 and 30 days of age; however, insertion and inflation of the tissue expander resulted in a statistically significant (p < 0.05) increase in posterior facial height, followed, in 30 days, by a significant increase in the length of the anterior cranial base. The remainder of the cranial base and the cranial vault grew without significant differences between the groups. This study demonstrates that changes in facial morphology can be effected in the growing skeleton through tissue expansion and provides further evidence to support the concept of an interrelated facial skeletal-basicranial-neurocranial axis.